Particle chains make quantum
wires

July 28/August 4, 2004

Computers must have the ability to transfer
data among different components. One of the difficult problems of building
a quantum computer is finding a way to transfer data stored as a property,
or quantum state, of an atom, electron or photon.

Researchers from the University of Cambridge in England, the National
University of Singapore and the Massachusetts Institute of Technology
have devised a relatively simple way to transfer data between quantum
bits, or qubits.

The method is a step toward building quantum computers, which
have the potential to solve certain types of very large problems many
orders of magnitude faster than is possible using classical computers.

The scheme calls for transporting quantum states that store information
without any operations, which change quantum properties. Particles like
atoms and electrons can be oriented in one of two directions, spin up
and spin down, which are akin to clockwise and counterclockwise rotation
of a spinning top.

Rather than using operations, the method calls for transferring
spin along a chain of particles, or quantum wire, as a result of creating
the chain. Like dominoes falling, a spin orientation introduced at one
end of the chain is passed through to the other end.

The researchers showed that it was possible to transfer quantum
states over a quantum wire, and also create chains in such a way that
a quantum register, or batch of information, can be inverted.

Most researchers agree that practical quantum computers are one
or two decades away. The work appeared in the May 7, 2004 issue of Physical
Review Letters.